Separation membrane module operation method, computer-readable recording medium recording a program, and fresh water generation system

Abstract

In a water production system for obtaining treated water by filtering treated water with the aid of a separation membrane module, the pressure difference (first resistance R1) between the pressure (P1) of the treated water supply section and the pressure (P3) of the backwash wastewater discharge section in the filtration process for filtering the treated water from the primary side to the secondary side of the separation membrane module, the pressure difference (second resistance R2) between the aforementioned pressure (P1) and the pressure (P2) of the treated water discharge section in the aforementioned filtration process, and the pressure difference (third resistance R3) between the aforementioned pressure (P1) and the aforementioned pressure (P3) in the back pressure washing process for pressurizing the water from the secondary side to the primary side of the aforementioned separation membrane module are calculated, and the blockage location of the aforementioned separation membrane module is determined based on the change or change rate of each of the resistances R1 to R3 obtained by the calculation from the initial value.

Description

Technical Field

[0001] The present invention relates to a separation membrane module and a fresh water generation system for treating natural water such as river water, lake water, and sea water, as well as sewage and industrial wastewater. Background Art

[0002] Membrane separation methods are widely used in a variety of fields due to their advantages, such as energy and space savings and improved filtered water quality. For example, microfiltration membranes and limited filtration membranes are used in water purification processes for producing industrial and tap water from river water, groundwater, and treated sewage water; in pretreatment processes for reverse osmosis membrane treatments for seawater desalination; and in manufacturing processes in the food industry.

[0003] When water to be treated is subjected to membrane filtration, the amount of pollutants accumulated on the membrane surface, in the membrane pores, and in the separation membrane module increases with the amount of treated water, causing a decrease in the amount of treated water or an increase in differential pressure to become a problem.

[0004] Therefore, physical cleaning methods have become practical, such as back-pressure washing, which uses pressure to push clean water (such as treated water) in the opposite direction of filtration to remove contaminants accumulated on the membrane surface and in the membrane pores; air washing, which introduces bubbles into the treated water side (primary side) of the membrane to vibrate the membrane, causing it to contact each other and thus scrape off attached substances on the membrane surface; and air-reverse simultaneous washing, which performs air washing and back-pressure washing simultaneously. However, after these washing methods, dirty water remains on the primary side of the separation membrane module, so the water in the separation membrane module is generally drained and then re-supplied with treated water.

[0005] Furthermore, in order to perform stable and long-term continuous membrane filtration operation, Patent Documents 1 and 2 propose the following method: controlling the washing time of back pressure washing according to the measured value of the membrane differential pressure during filtration, or controlling the physical washing frequency such as back pressure washing and air washing.

[0006] On the other hand, there are cases where, even if the above-mentioned washing process is performed, only the easily washable parts of the separation membrane module are washed, resulting in insufficiently washed parts, or where insufficiently washed parts are generated due to the influx of highly turbid water such as heavy rain at a level higher than expected, making it difficult to operate the membrane filtration stably. As a solution to such a problem, Patent Document 3 proposes the following method: determining the blockage site of the accumulated material in the separation membrane module and efficiently removing the accumulated material. Specifically, the pressure difference between the inlet and outlet sides of the primary side of the separation membrane module in the process of supplying treated water to the primary side of the separation membrane module (water supply process), the pressure difference between the primary and secondary sides of the separation membrane module in the filtration process of pressure-feeding the treated water from the primary side of the separation membrane module to the secondary side, and the pressure difference between the secondary and primary sides of the separation membrane module in the back-pressure washing process of permeating from the secondary side of the separation membrane module to the primary side are utilized, and then the calculation of combining the respective pressure differences is performed to determine the blockage site.

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 11-169851.

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 11-019485.

[0009] Patent Document 3: International Publication No. 2018 / 026020.

[0010] The location of a blockage in a separation membrane module can also be determined using the conventional method for determining the location of a blockage in a separation membrane module described in Patent Document 3. However, this method requires operational data from at least three processes: the water supply process, the filtration process, and the back-pressure washing process. Furthermore, determination requires a complex calculation combining the operational data from each process. Furthermore, when the water supply process is performed after the drainage process, the flow rate and pressure tend to become unstable immediately after the water supply process begins. Therefore, obtaining stable data requires a long time, and this method is not applicable to operations in which the three processes are not aligned, such as when neither the water supply nor the drainage process is performed. Summary of the Invention

[0011] Therefore, an object of the present invention is to provide a method for identifying a clogged portion of a separation membrane module more simply and quickly than conventional methods with higher accuracy.

[0012] In order to solve the above-mentioned problems, the present invention has the following features.

[0013] (1) A method for operating a separation membrane module, wherein the method for operating the separation membrane module is as follows: in a water production system for obtaining treated water by filtering treated water through the separation membrane module, the blockage position of the separation membrane module is determined based on the resistance of the lower portion of the separation membrane module, the filtration resistance of the separation membrane portion, and the resistance of the upper portion of the separation membrane module. The method for operating the separation membrane module is characterized in that the separation membrane module is composed of a cylindrical shell with a separation membrane inserted therein, a treated water supply portion for supplying the treated water is provided at the lower portion of the separation membrane module as the primary side, a treated water discharge portion for discharging the treated water is provided at the upper portion as the secondary side, a backwash wastewater discharge portion for discharging backpressure washing wastewater is provided at the upper side of the cylindrical shell as the primary side and is connected to the outside of the separation membrane. The water production system is provided with a device for measuring the pressure of the treated water supply portion. A supply pressure sensor for measuring pressure P1, a secondary side pressure sensor for measuring pressure P2 of the treated water discharge section, and a primary side outlet pressure sensor for measuring pressure P3 of the backwash wastewater discharge section are used. The pressure difference ΔP1 between the P1 and the P3 in the filtration process of filtering the treated water from the primary side to the secondary side of the separation membrane module is set as the first resistance R1, the pressure difference ΔP2 between the P3 and the P2 in the filtration process is set as the second resistance R2, and the pressure difference ΔP3 between the P1 and the P3 in the back pressure washing process of pressurizing the water from the secondary side to the primary side of the separation membrane module is set as the third resistance R3 for calculation. The blockage location of the separation membrane module is determined based on the change amount or change rate of each of the first resistance R1 to the third resistance R3 obtained by the calculation from the initial value.

[0014] (2) The method for operating the separation membrane module according to (1), wherein the pressure P3 in the filtration step and the pressure P1 in the back pressure washing step are static pressures.

[0015] (3) The method for operating the separation membrane module as described in (1) or (2), characterized in that the changes of the first resistance R1, the second resistance R2, and the third resistance R3 from their initial values ​​are compared. When the change of the first resistance R1 from its initial value is larger than the change of the second resistance R2 and the change of the third resistance R3 from their initial values, or when the change of the first resistance R1 from its initial value is larger than the set value, at least one of the following controls A to C is performed: A is a control a for raising and lowering the liquid level on the primary side of the separation membrane module and performing air washing; B is a control b for lengthening the process time of the drainage process; C is a pressurized drainage control c for pressurizing the primary side of the separation membrane module with the aid of air to drain water during the drainage process.

[0016] (4) The method for operating the separation membrane module as described in (1) or (2), characterized in that the respective rates of change of the aforementioned first resistance R1, the aforementioned second resistance R2, and the aforementioned third resistance R3 from their initial values ​​are compared. When the rate of change of the aforementioned first resistance R1 from the initial value is greater than the rates of change of the second resistance R2 from the initial value and the rates of change of the third resistance R3 from the initial value, or when the rate of change of the aforementioned first resistance R1 from the initial value is greater than the set value, at least one of the following controls A to C is performed: A is a control a for raising and lowering the liquid level on the primary side of the aforementioned separation membrane module and performing air washing; B is a control b for lengthening the process time of the drainage process; C is a pressurized drainage control c for pressurizing the primary side of the separation membrane module with the help of air to drain water during the drainage process.

[0017] (5) The method for operating the separation membrane module as described in (1) or (2), characterized in that the changes of the first resistance R1, the second resistance R2, and the third resistance R3 from their respective initial values ​​are compared. When the change of the second resistance R2 from its initial value is larger than the change of the first resistance R1 and the change of the third resistance R3 from their initial value, or when the change of the second resistance R2 from its initial value is larger than the set value, at least one of the following controls F to H is performed: F is a control f for supplying chemical solution to the separation membrane module to wash the separation membrane module; G is a control g for changing at least one of the back pressure washing time and the air washing time; H is a control h for changing at least one of the back pressure washing flow rate during the back pressure washing process and the air volume during the air washing process.

[0018] (6) The method for operating the separation membrane module as described in (1) or (2), characterized in that the respective rates of change of the first resistance R1, the second resistance R2, and the third resistance R3 from their initial values ​​are compared. When the rate of change of the second resistance R2 from its initial value is greater than the rates of change of the first resistance R1 and the third resistance R3 from their initial values, or when the rate of change of the second resistance R2 from its initial value is greater than the set value, at least one of the following controls F to H is performed: F is a control f for supplying a chemical solution to the separation membrane module to wash the separation membrane module; G is a control g for changing at least one of the back pressure washing time and the air washing time; H is a control h for changing at least one of the back pressure washing flow rate during the back pressure washing process and the air washing amount during the air washing process.

[0019] (7) The method for operating the separation membrane module as described in (1) or (2), characterized in that the changes of the first resistance R1, the second resistance R2, and the third resistance R3 from their initial values ​​are compared. When the change of the third resistance R3 from the initial value is larger than the change of the first resistance R1 and the change of the second resistance R2 from the initial value, or when the change of the third resistance R3 from the initial value is larger than the set value, at least one of the following controls D to E is performed: D is a control d for reversely supplying treated water from the nozzle that discharges the washing wastewater of the separation membrane module; E is a control e for back-pressure washing after discharging the water on the primary side of the separation membrane module to make it empty.

[0020] (8) The method for operating the separation membrane module as described in (1) or (2), characterized in that the respective rates of change of the first resistance R1, the second resistance R2, and the third resistance R3 from their initial values ​​are compared. When the rate of change of the third resistance R3 from the initial value is greater than the rate of change of the first resistance R1 and the rate of change of the second resistance R2 from the initial value, or when the rate of change of the third resistance R3 from the initial value is greater than the set value, at least one of the following controls D to E is performed: D is a control d for reversely supplying treated water from the nozzle that discharges the washing wastewater of the separation membrane module; E is a control e for back-pressure washing after discharging the water on the primary side of the separation membrane module to an empty state.

[0021] (9) The method for operating a separation membrane module as described in any one of (3) to (8), characterized in that at least one of the pressure change rate on the primary side and the drainage flow rate in the separation membrane module in the drainage process is selected as an indicator and combined with the aforementioned first resistance R1, the aforementioned second resistance R2, and the aforementioned third resistance R3 to determine the blockage location of the aforementioned separation membrane module, and the aforementioned drainage process discharges the treated water from the lower part of the primary side of the separation membrane module to the outside of the system.

[0022] (10) The method for operating the separation membrane module as described in (1) or (2), characterized in that the pressure difference ΔP4 between the aforementioned P2 and the aforementioned P1 in the aforementioned back pressure washing process is further calculated as the fourth resistance R4, and when the difference R2-R4 between the aforementioned second resistance R2 and the aforementioned fourth resistance R4 is larger than the set value, at least one of the following controls G to I is performed, G is a control for changing at least one of the back pressure washing time and the air washing time; H is a control for changing at least one of the back pressure washing flow rate during the back pressure washing process and the air volume during the air washing process; I is a control for changing at least one of the water supply process time and the water supply flow rate.

[0023] (11) The method for operating the separation membrane module as described in (1) or (2), characterized in that the pressure difference ΔP4 between the aforementioned P2 and the aforementioned P1 in the aforementioned back pressure washing process is further calculated as the fourth resistance R4, and when the ratio R2 / R4 of the aforementioned second resistance R2 and the aforementioned fourth resistance R4 is larger than the set value, at least one of the following controls G to I is performed, G is a control for changing at least one of the back pressure washing time and the air washing time; H is a control for changing at least one of the back pressure washing flow rate during the back pressure washing process and the air volume during the air washing process; I is a control for changing at least one of the water supply process time and the water supply flow rate.

[0024] (12) The method for operating the separation membrane module as described in (10) or (11), characterized in that the filtration flow rate during the aforementioned filtration step and the backwash flow rate during the aforementioned backpressure washing step are the same.

[0025] (13) The method for operating the separation membrane module according to any one of (10) to (12), characterized in that:

[0026] The second resistance R2 and the fourth resistance R4 are resistance values ​​calculated based on the pressure difference, flow rate data, and water temperature data.

[0027] (14) A recording medium readable by a computer having a management program for a water production system recorded thereon, wherein in order to determine the blockage position of a separation membrane module of a water production system that obtains treated water by filtering treated water through a separation membrane module, the computer functions as a blockage position determining mechanism that determines the blockage position of the separation membrane module based on the resistance of the lower portion of the separation membrane module, the filtration resistance of the separation membrane portion, and the resistance of the upper portion of the separation membrane module. The recording medium readable by a computer having a management program for a water production system recorded thereon is characterized in that the separation membrane module is composed of a cylindrical shell into which a separation membrane is inserted, a treated water supply portion for supplying the treated water is provided at the lower portion of the separation membrane module as the primary side, a treated water discharge portion for discharging the treated water is provided at the upper portion as the secondary side, and a backwash wastewater discharge portion for discharging backpressure washing wastewater is provided at the upper side of the cylindrical shell as the primary side and is connected to the outside of the separation membrane. The water production system has a device for measuring the pressure of the treated water. The supply pressure sensor for measuring the pressure P1 of the water supply section, the secondary side pressure sensor for measuring the pressure P2 of the aforementioned treated water discharge section, and the primary side outlet pressure sensor for measuring the pressure P3 of the aforementioned backwash wastewater discharge section enable the aforementioned computer to function as a differential operation mechanism and a blockage location determination mechanism. The aforementioned differential operation mechanism sets the pressure difference ΔP1 between the aforementioned P1 and the aforementioned P3 in the filtration process of filtering the aforementioned treated water from the primary side to the secondary side of the separation membrane module as the first resistance R1, sets the pressure difference ΔP2 between the aforementioned P3 and the aforementioned P2 in the aforementioned filtration process as the second resistance R2, and sets the pressure difference ΔP3 between the aforementioned P1 and the aforementioned P3 in the back pressure washing process of pressurizing from the secondary side to the primary side of the aforementioned separation membrane module as the third resistance R3 for calculation. The aforementioned blockage location determination mechanism determines the blockage location of the aforementioned separation membrane module based on the change amount or change rate of each value obtained by the aforementioned differential operation mechanism from the initial value.

[0028] (15) The computer-readable recording medium having the fresh water system management program recorded thereon as described in (14) is characterized in that the P3 in the filtration step and the P1 in the back pressure washing step are static pressure.

[0029] (16) A water production system, in which, in order to determine the blockage position of the separation membrane module of the water production system that obtains treated water by filtering the treated water through the separation membrane module, a computer is made to function as a blockage position determination mechanism that determines the blockage position of the separation membrane module based on the resistance of the lower part of the separation membrane module, the filtration resistance of the separation membrane part, and the resistance of the upper part of the separation membrane module. The water production system is characterized in that the separation membrane module is composed of a cylindrical shell with a separation membrane inserted, a treated water supply part for supplying the treated water is provided at the lower part of the separation membrane module as the primary side, a treated water discharge part for discharging the treated water is provided at the upper part as the secondary side, and a backwash wastewater discharge part for discharging backpressure washing wastewater is provided at the upper part of the side surface of the cylindrical shell as the primary side and is connected to the outside of the separation membrane. The water production system is provided with a supply pressure sensor for measuring the pressure P1 of the treated water supply part, a pressure sensor for measuring the pressure P1 of the treated water supply part, a pressure sensor for measuring the pressure P2 of the treated water supply part, a pressure sensor for measuring the pressure P3 of the treated water supply part, a pressure sensor for measuring the pressure P4 of the treated water supply part, a pressure sensor for measuring the pressure P5 of the treated water supply part, a pressure sensor for measuring the pressure P6 of the treated water supply part, a pressure sensor for measuring the pressure P7 of the treated water supply part, a pressure sensor for measuring the pressure P8 of the treated water supply part, a pressure sensor for measuring the pressure P9 of the treated water supply part, a pressure sensor for measuring the pressure P1 ...2 of the treated water supply part, a pressure sensor for A secondary-side pressure sensor for measuring the pressure P2 of the treated water discharge section and a primary-side outlet pressure sensor for measuring the pressure P3 of the aforementioned backwash wastewater discharge section enable the aforementioned computer to function as a differential operation mechanism and a blockage location determination mechanism. The aforementioned differential operation mechanism sets the pressure difference ΔP1 between the aforementioned P1 and the aforementioned P3 in the filtration process of filtering the aforementioned treated water from the primary side to the secondary side of the separation membrane module as the first resistance R1, sets the pressure difference ΔP2 between the aforementioned P3 and the aforementioned P2 in the aforementioned filtration process as the second resistance R2, and sets the pressure difference ΔP3 between the aforementioned P1 and the aforementioned P3 in the back-pressure washing process of pressurizing the water from the secondary side to the primary side of the aforementioned separation membrane module as the third resistance R3 for calculation. The aforementioned blockage location determination mechanism determines the blockage location of the aforementioned separation membrane module based on the change amount or change rate of each of the first resistance R1 to the third resistance R3 obtained by the aforementioned differential operation mechanism from the initial value.

[0030] (17) The fresh water generation system according to (16), characterized in that the P3 in the filtration step and the P1 in the back pressure washing step are static pressure.

[0031] Effects of the Invention

[0032] According to the present invention, compared with conventional methods, the clogged portion in the separation membrane module can be identified more simply, quickly, and accurately, and the separation membrane module can be cleaned efficiently according to the clogged portion, thereby stably obtaining treated water over a long period of time. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic flow chart showing an example of a fresh water generation system to which the present invention is applied.

[0034] Figure 2 This is a schematic diagram showing an example of a separation membrane module to which the present invention is applied.

[0035] Figure 3It is a schematic diagram showing an embodiment of the present invention.

[0036] Figure 4 It is a schematic diagram showing an embodiment of the present invention.

[0037] Figure 5 is a schematic diagram showing an embodiment of the present invention, Figure 5 (a) represents the full filtration process, Figure 5 (b) shows the reverse pressure washing step. DETAILED DESCRIPTION

[0038] Hereinafter, the present invention will be described in more detail based on the embodiments shown in the drawings. However, the present invention is not limited to the following embodiments.

[0039] The present invention relates to a method for operating a separation membrane module, a management program, and a water production system, including a method for determining a blockage location in a separation membrane module. Figure 1 As shown, there are provided a treated water supply pump 1 for supplying treated water, a treated water supply valve 2 which is opened when the treated water is supplied, a separation membrane module 3 for filtering the treated water, a backwash drain valve 4 which is opened in the case of backpressure washing or air washing, a treated water discharge valve 5 which is opened during membrane filtration, a treated water storage tank 6 for storing treated water, a backpressure washing pump 7 which supplies treated water to the separation membrane module 3 for backpressure washing, a backpressure washing valve 8 which is opened during backpressure washing, a drug liquid supply pump 9 which supplies drug liquid to the treated water or the separation membrane module, a drug liquid storage tank 10 which stores drug liquid, and an air supply source for air washing of the separation membrane module 3. The components include a blower 11 for supplying air to the lower portion of the separation membrane module 3 for air washing, an air washing valve 12 opened to supply air to the lower portion of the separation membrane module 3 for air washing, a drain valve 13 opened to discharge the treated water or wash wastewater from the primary side of the separation membrane module 3, a treated water supply valve 14 to the primary side, a treated water bypass valve 15, a primary side supply pressure sensor 16 for measuring the pressure (P1) of the treated water supply section, a primary side outlet pressure sensor 17 for measuring the pressure (P3) of the backwash wastewater discharge section, a secondary side pressure sensor 18 for measuring the pressure (P2) of the treated water discharge section, and a drain flow rate sensor 19. The treated water refers to the solution treated by the separation membrane module, and examples thereof include river water, groundwater, seawater, sewage treatment water, factory wastewater, and culture medium.

[0040] The pore size of the separation membrane used in the separation membrane module 3 is not particularly limited as long as it is porous. However, depending on the desired properties and amount of the water to be treated, an MF membrane (microfiltration membrane) or an UF membrane (ultrafiltration membrane) can be used, or a combination of the two. For example, to remove turbid components, Escherichia coli, Cryptosporidium, etc., either an MF membrane or a UF membrane can be used. However, to also remove viruses and high-molecular organic matter, a UF membrane is preferably used. The shape of the separation membrane includes hollow fiber membranes, flat membranes, tubular membranes, monolithic membranes, etc., but any type can be used.

[0041] As the material of separation membrane, preferably, including at least one selected from the group consisting of inorganic materials such as polyethylene, polypropylene, polyacrylonitrile, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, polytetrafluoroethylene, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer and chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride, polysulfone, cellulose acetate, polyvinyl alcohol and polyether sulfone, ceramics, and then, according to the viewpoint of membrane strength, chemical resistance, more preferably polyvinylidene fluoride (PVDF), according to the viewpoint that hydrophilicity is high and fouling resistance is strong, more preferably polyacrylonitrile. In addition, separation membrane module 3 has a shell inserted with separation membrane, at least with processed water supply portion, backwash wastewater discharge portion and treated water discharge portion. As the shape of shell, for cylindrical, polygonal type etc., is not particularly limited.

[0042] Figure 2 An example of a separation membrane module to which the present invention is applied is shown, in which a plurality of hollow fiber membranes are inserted as separation membranes 21 in a cylindrical shell 20, and the hollow fiber membranes are bonded and fixed by potting material 22 at both ends of the cylindrical shell 20. A bonding and fixing portion is provided at the upper portion of the membrane module, and the hollow portion of the hollow fiber membrane is open, and a removable cap 23 is installed. On the other hand, a bonding and fixing portion is provided at the lower portion of the membrane module, and the ends of the hollow fiber membranes are blocked by potting material 22. On the side of the cylindrical shell 20, a lower side nozzle 24 and an upper side nozzle 25 that are connected to the outside of the hollow fiber membrane are provided on the inner side compared to the bonding and fixing portions at both ends of the cylindrical shell 20. The lower side nozzle 24 can be used as a treated water supply portion, and the upper side nozzle 25 can be used as an air exhaust portion, a treated water discharge portion, and a backwash wastewater discharge portion during back pressure washing. Lower nozzle 27 serves as an air supply for air scrubbing and a backwash wastewater discharge port, so a through-hole 28 is provided in the lower adhesive fixing portion of the membrane module. During filtration operation, the supplied treated water is filtered by the hollow fiber membranes, and treated water is obtained from upper nozzle 26 (treated water discharge port). Furthermore, when operating without the lower side nozzles or in a module configuration without lower side nozzles, lower nozzle 27 can serve not only as an air supply and backwash wastewater discharge port, but also as a treated water supply port. Figure 1The figure shows a method of using the lower nozzle as a treated water supply part. In addition, the filling rate of the hollow fiber membrane in the cylindrical shell is generally not less than 30% and not more than 80%. In the case of too low a filling rate, the hollow fiber membrane shakes excessively at the interface of the adhesive fixing part when a high flow rate of water flows through, and there is a possibility that the hollow fiber membrane breaks. In addition, if the filling rate is too high, it will be difficult to insert the hollow fiber membrane bundle into the cylindrical shell during the manufacturing process of the hollow fiber membrane module. Here, the filling rate of the hollow fiber membrane refers to the ratio of the portion occupied by the hollow fiber membrane contained in the hollow fiber membrane bundle to the portion surrounded by the hollow fiber membrane arranged at the outermost periphery of the hollow fiber membrane bundle in the small diameter portion.

[0043] The material of the cylindrical shell 20 is not particularly limited. Examples include containers made of resins such as ABS, polypropylene, polyvinyl chloride, and polycarbonate; containers made of fiber-reinforced resins such as epoxy resin and polyurethane resin reinforced with reinforcing fibers such as glass fiber and carbon fiber; and containers made of metals such as stainless steel. Examples of the material of the potting material 22 include epoxy resin and polyurethane.

[0044] The “primary side” refers to the side of the space partitioned by the separation membrane where the water to be treated is supplied, and the “secondary side” refers to the side where the treated water is supplied after being filtered by the separation membrane.

[0045] Regarding the blockage site determination according to the embodiment of the present invention, for example, Figure 3 As shown, the system is characterized by having the following mechanisms: First, the operation data recording mechanism 40 and the blockage location identification program 32 are introduced into the computer 31 that receives the operation data from the fresh water system 30 .

[0046] Figure 1In the illustrated fresh water generation system 30, a treated water supply pump 1 causes treated water to flow, and the treated water supply valve 2 and backwash drain valve 4 are opened to supply treated water to the primary side of the separation membrane module 3. During this treated water supply process, after the primary side is filled with treated water, the backwash drain valve 4 is closed and the treated water discharge valve 5 is opened, thereby transitioning to the filtration process, in which filtration is performed using the separation membranes within the separation membrane module 3. Alternatively, the water supply process can be omitted. Although not shown, if an exhaust valve is provided between the backwash drain valve 4 and the upper side nozzle 25 of the separation membrane module, even if air is present on the primary side of the separation membrane module 3, the backwash drain valve 4 is closed, the treated water discharge valve 5 is opened, and the filtration process begins, air can be automatically expelled. During the filtration process, treated water is transferred from the secondary side of the separation membrane module 3 via the treated water discharge valve 5 to the treated water storage tank 6. For full filtration, the backwash drain valve 4, backpressure wash valve 8, air wash valve 12, and drain valve 13 are all closed. The pressures on the primary and secondary sides of the separation membrane module during the filtration process are measured by the primary-side supply pressure sensor 16, the primary-side outlet pressure sensor 17, and the secondary-side pressure sensor 18, respectively, and recorded in the operation data recording device 40. Although not shown, operation data such as the filtration flow rate and water temperature are also measured and recorded in the operation data recording device 40.

[0047] There are two filtration methods: full-flow filtration and cross-flow filtration. In the cross-flow filtration method, instead of fully closing the backwash drain valve 4 during the filtration process, the backwash drain valve 4 is adjusted in opening, allowing a portion of the treated water to be discharged while filtering. Either filtration method can be used, but full-flow filtration modules are preferred due to their low energy consumption. Furthermore, as described later, full-flow filtration modules are also preferred for determining blockage in separation membrane modules according to embodiments of the present invention.

[0048] As the filtration time passes, the filtration resistance of the separation membrane module increases. That is, in the case of constant flow filtration operation, the pressure difference between the primary and secondary sides of the membrane module (generally "P2-P1") increases. Generally, to suppress this increase, physical washing is performed regularly, and operation is repeated while filtration and physical washing are performed. In addition, the filtration time is preferably appropriately set according to the properties of the treated water and the membrane filtration flow rate, but the filtration time can also be continued until a predetermined membrane filtration differential pressure is reached.

[0049] In physical washing, generally, filtration is temporarily stopped and the process is carried out in the order of reverse pressure washing, air washing, drainage, and water supply. However, the reverse pressure washing and air washing processes can also be carried out at the same time, the reverse pressure washing process can be carried out after the drainage process, or a certain process can be omitted or carried out multiple times.

[0050] After the filtration process is completed, the treated water supply pump 1 is stopped, the treated water supply valve 2 and the treated water discharge valve 5 are closed, the back-pressure washing valve 8 and the back-washing drain valve 4 are opened, and the back-pressure washing pump 7 is activated, thereby shifting to the back-pressure washing process of pressure-feeding from the secondary side to the primary side of the separation membrane module. The pressures on the primary and secondary sides of the separation membrane module during the back-pressure washing process are measured using the primary-side supply pressure sensor 16, the primary-side outlet pressure sensor 17, and the secondary-side pressure sensor 18, respectively, and recorded in the operation data recording mechanism 40. In addition, although not shown in the figure, the operation data recording mechanism 40 is not particularly limited as long as it is data related to the operation. For example, the flow rate and water temperature of the back-pressure washing water are also recorded in the operation data recording mechanism 40.

[0051] There are no particular limitations on the back-pressure wash water used. It is preferred to use treated water obtained by filtering the treated water through a separation membrane module, as in this embodiment. However, industrial water, purified water, tap water, RO membrane permeate, or pure water may also be used. Furthermore, the back-pressure wash time is not particularly limited, but is preferably within the range of 1 to 120 seconds. If the back-pressure wash time is less than 1 second, sufficient washing effect will not be achieved. If it exceeds 120 seconds, the operating efficiency of the separation membrane module and the water recovery rate will decrease.

[0052] After the back-pressure washing step is completed, the back-pressure washing pump 7 is stopped, the back-pressure washing valve 8 is closed, and the air washing valve 12 is opened to transfer to the air washing step, in which the blower 11 is operated to supply air to the separation membrane module 3 for washing. The air washing time is not particularly limited, but is preferably within the range of 1 to 120 seconds. If the back-pressure washing time is less than 1 second, sufficient washing effect cannot be achieved. If it exceeds 120 seconds, the operating efficiency of the separation membrane module will decrease. Alternatively, the air washing valve 12 can be opened midway through the back-pressure washing step to operate the blower 11 and initiate the air washing step.

[0053] After the air scrubbing process is completed, the blower 11 is stopped, the air scrubbing valve 12 is closed, and the drain valve 13 is opened, transitioning to the drainage process in which all the wastewater accumulated in the separation membrane module 3 is drained. During the drainage process, the backwash drain valve 4 and drain valve 13 are opened to allow the primary-side treated water to be discharged from the lower portion of the separation membrane module. The primary-side pressure and drain flow rate within the separation membrane module during the drainage process are measured using the primary-side supply pressure sensor 16 or drain flow rate sensor 19 and recorded in the operating data recording device 40. The process then returns to the treated water supply process, and membrane filtration operation continues.

[0054] The present invention is characterized in that Figure 3For example, the operation data recorded in the operation data recording means 40 are processed by the difference calculation means 41 and the drainage process calculation means 46 included in the blockage location identification program 32 , and the blockage location of the separation membrane module is identified by the blockage location identification means 42 .

[0055] Specific methods included in the difference calculation unit 41 include, for example, difference calculation methods 1 to 4.

[0056] Differential calculation method 1 obtains the pressure difference (ΔP1) between the pressure (P1) of the treated water supply part and the pressure (P3) of the backwash wastewater discharge part in the filtration process of filtering the treated water from the primary side to the secondary side of the separation membrane module as the first resistance R1.

[0057] Differential calculation method 2 obtains the pressure difference (ΔP2) between the pressure (P3) of the backwash wastewater discharge part and the pressure (P2) of the treated water discharge part in the filtration process of filtering the treated water from the primary side to the secondary side of the separation membrane module as the second resistance R2.

[0058] Differential calculation method 3 obtains the pressure difference (ΔP3) between the pressure (P1) of the treated water supply part and the pressure (P3) of the backwash wastewater discharge part in the backwashing process of pressure-feeding from the secondary side to the primary side of the separation membrane module as the third resistance R3.

[0059] The difference calculation method 4 obtains the pressure difference (ΔP4) between the pressure (P2) of the treated water discharge part and the pressure (P1) of the treated water supply part in the back pressure washing process of pressure-feeding from the secondary side to the primary side of the separation membrane module as the fourth resistance R4.

[0060] When calculating the pressure difference, P3 in the filtration process and P1 in the backwash process are preferably static pressures. If the pressure gauges measuring the pressures P1 to P3 are installed at different heights, it is preferable to perform corrections that take into account the head difference.

[0061] The first resistance R1 to the fourth resistance R4 are based on the following conditions: when the fresh water system performs a constant flow filtration operation (i.e., the filtration process and the back pressure washing process are continuously operated at the same flow rate from the start of the operation).

[0062] (During the filtration process)

[0063] (During the filtration process)

[0064] (Back pressure washing process)

[0065] (Back pressure washing process)

[0066] Calculation is performed. In addition, when the aforementioned second resistance R2 and the aforementioned fourth resistance R4 are pressure difference data, it is preferred to set the flow rate of the filtration process and the back-pressure washing process to be the same, or to perform a correction of the pressure difference based on the flow rate. When the flow rate (flow rate) of the filtration process and the back-pressure washing process is inconsistent or when the filtration flow rate such as constant pressure filtration operation changes over time during continuous operation, it is preferred to implement a correction of each pressure difference ΔP taking into account the flow rate during pressure measurement. When the pressure difference is corrected according to the flow rate, calculation can be performed by pressure difference / flow rate. When comparing the pressure differences obtained at different water temperature periods, it is preferred to further perform viscosity correction of the differential pressure data based on the water temperature.

[0067] In addition, although the details will be described later, the second resistance R2 and the fourth resistance R4 are indicators that represent the filtration resistance of the separation membrane portion. Preferably, the resistance value is calculated based on the pressure difference data, the flow rate data, and the water temperature data in a manner that allows comparison of the second resistance R2 and the fourth resistance R4 that make the premise conditions consistent even when the measurement conditions (flow rate, water temperature) are different. This is calculated using the following formula. In addition, the first resistance R1 and the third resistance R3 are indicators that represent the flow path resistance (pressure loss) on the primary side of the separation membrane module, and they change according to the flow rate conditions during the filtration process or the back pressure washing process. Therefore, the pressure difference data or the water temperature correction value of the pressure difference data obtained by making the flow rate conditions consistent can be used as the first resistance R1 and the third resistance R3.

[0068] Second resistance R2 (1 / m) = ΔP2 (Pa) / (filtered water viscosity (Pa·s) × filtration flow rate (m / s))

[0069] 4th resistance R4 (1 / m) = ΔP4 (Pa) / (filtered water viscosity (Pa·s) × backwash flow rate (m / s))

[0070] According to the changes in the resistances (pressure differences) obtained through the above-mentioned calculation processing, the blockage parts of the separation membrane module can be divided into roughly three parts: the lower part of the primary side of the separation membrane module (near the treated water supply part), the separation membrane, and the upper part of the primary side of the separation membrane module (near the backwash wastewater discharge part). Furthermore, regarding the blockage of the separation membrane part, the inventors found that it can be divided into two types of blockage. The blockage of the primary side of the separation membrane module (the increase in resistance due to the accumulation of turbidity) occurs, for example, when the separation membrane module only washes the parts that are easy to wash and produces insufficiently washed parts, or when high turbidity water flows in to a degree greater than expected due to heavy rain, resulting in insufficient physical washing. The blockage part varies according to the shape, specific gravity, operating conditions, shape, etc. of the turbidity, but due to the flow of water in the separation membrane module in the above-mentioned washing process, the accumulation of turbidity does not occur near the center of the primary side of the separation membrane module (between the separation membranes), and occurs roughly in the lower part of the primary side or the upper part of the primary side of the separation membrane module. If it is Figure 2 In the illustrated separation membrane module configuration, water flows in and out of the lower side nozzles 24 or lower nozzles 27, which serve as the treated water supply unit. Therefore, turbidity easily accumulates between the hollow fiber membranes and near the through-holes 28 at the lower portion of the primary side of the separation membrane module, i.e., near the lower potting material. Furthermore, water sometimes flows in and out of the upper side nozzles 25, which serve as the backwash wastewater discharge unit, or during the air scrubbing process, turbidity sometimes accumulates between the hollow fiber membranes at the upper portion of the primary side of the separation membrane module, i.e., near the upper potting material. The first clogging mode of the separation membrane unit is as follows: as filtration continues, the substances to be removed in the treated water adhere to / accumulate within the membrane pores or on the membrane surface, thereby clogging the separation membrane pores or substantially reducing the pore diameter, thereby increasing the resistance of the separation membrane unit. The second clogging method is as follows: a portion of the accumulation layer of attached substances on the surface of the separation membrane is fixed to the separation membrane and acts like a check valve, becoming a resistance to the separation membrane part during the filtration process, but not becoming a resistance during the reverse pressure washing process (the attached substances are not completely removed from the membrane and remain).

[0071] The conventional method for determining the location of a blockage in a separation membrane module described in Patent Document 3 can also basically determine the location of the blockage. However, this method requires operating data from at least three processes: the water supply process, the filtration process, the backwash process, or the drainage process. Furthermore, the operation data from each process must be combined to determine the location of the blockage, resulting in a complex calculation process. Furthermore, when the water supply process is performed after the drainage process, the flow rate and pressure tend to become unstable immediately after the water supply process begins, so obtaining stable data requires a long time. Furthermore, the method cannot be applied to operations in which the three processes are not aligned, such as operations in which neither the water supply process nor the drainage process is performed. On the other hand, the differential calculation method according to an embodiment of the present invention can determine the location of the blockage in the separation membrane module based on the operating data from a single process. Furthermore, since only the operating data from the filtration process and the backwash process are used, the method is relatively concise and can determine the location of the blockage in the separation membrane module quickly and with higher accuracy than before.

[0072] like Figure 5As shown in (a), the first resistance R1 of the differential operation method 1 is an indicator of the degree of blockage (increase in resistance) near the lower part 3a of the primary side of the separation membrane module in the case of full filtration. R1 can be calculated based on the difference (ΔP1) in the pressure between the primary inlet side and the primary outlet side of the separation membrane module during the filtration process, and represents the flow path resistance (pressure loss) of the primary side of the separation membrane module. In the case of full filtration, P3 is the static pressure, so the treated water hardly flows in the upper part 3b of the primary side of the separation membrane module near the P3 measuring part (near the backwash wastewater discharge part), so no pressure loss occurs. That is, when the R1 calculated in the full filtration process increases over time, it can be regarded as an increase in the blockage of the lower part 3a of the primary side of the separation membrane module (near the treated water supply part), which is the part where the treated water flows and turbidity is easily accumulated. Furthermore, when measuring P1 and P3 with the backwash drain valve 4 open during the treated water supply process, such as in cross-flow filtration, P1 and P3 represent dynamic pressures. In this case, the calculated R1 includes the flow resistance generated in the upper primary portion of the separation membrane module in addition to the lower primary portion of the separation membrane module. Therefore, in cross-flow filtration, the degree of blockage in the lower primary portion of the separation membrane module can be quantified by subtracting the flow resistance generated in the upper primary portion of the separation membrane module from the calculated first resistance R1. For example, if the third resistance R3 calculated in differential calculation method 3 is used, the result of the calculation of R1-R3 is the blockage index for the lower primary portion of the separation membrane module.

[0073] In addition, if Figure 5As shown in (a), the second resistance R2 of the differential calculation method 2 is an index of clogging of the first separation membrane section in the case of full filtration, that is, an index indicating the degree of clogging (increase in resistance) of the separation membrane section during the filtration process of the separation membrane module. R2 can be calculated based on the pressure difference (ΔP2) between the pressure (P3) of the backwash wastewater discharge section and the pressure (P2) of the treated water discharge section during the filtration process. As mentioned above, in the case of full filtration, the pressure (P3) of the backwash wastewater discharge section is static pressure. That is, it does not include the flow path resistance generated on the primary side of the separation membrane module, so R2 can be regarded as the filtration resistance generated at the separation membrane 21. In the case of cross-flow filtration, the pressure (P3) of the backwash wastewater discharge section is dynamic pressure. When there is clogging on the upper part of the primary side of the separation membrane module, P3 is the value of pressure loss. The pressure measured based on P3 is lower than the pressure value actually used for filtration, so R2 in cross-flow filtration overestimates the filtration resistance of the separation membrane 21. Therefore, in cross-flow filtration, the calculated R2 must be supplemented with the flow resistance generated in the upper portion of the primary side of the separation membrane module. For example, the third resistance R3 calculated using differential calculation method 3 can be used to calculate R2 + R3 to obtain a clogging index for the first separation membrane section. Furthermore, while P2 - P1 is generally used as an indicator of the operating differential pressure, in this case, the effect of clogging in the lower portion of the primary side of the separation membrane module is also included, in addition to clogging of the separation membrane.

[0074] like Figure 5 As shown in (b), the third resistance R3 of the differential operation method 3 is an indicator of the degree of blockage (increase in resistance) of the upper part 3b of the primary side of the separation membrane module. The pressure (P1) of the treated water supply part is measured as the primary side inlet side of the separation membrane module in the back pressure washing process, and the pressure (P3) of the backwash wastewater discharge part is measured as the primary side outlet side, and it can be calculated based on the difference (ΔP3) between these pressures. In addition, the pressure (P1) of the treated water supply part is preferably measured as static pressure. In the case where the backwash drain valve 4 in the valve of the separation membrane module is opened and other valves are closed to perform the back pressure washing process, the pressure (P1) of the treated water supply part can be measured as the pressure on the primary side inlet side of the separation membrane module, and the pressure (P3) of the backwash wastewater discharge part can be measured as the pressure (static pressure) on the primary side outlet side of the separation membrane module. As a result, no flow path resistance is generated in the lower part of the primary side of the separation membrane module, so R3 can be regarded as the flow path resistance generated in the upper part of the primary side of the separation membrane module. In addition, for example Figure 1In the illustrated apparatus, in the back-pressure washing process, in which back-pressure washing wastewater is discharged from the treated water supply, the back-pressure washing valve 8 and drain valve 13 are opened, while the other valves are closed. The pressure (P3) at the back-wash wastewater discharge port represents the static pressure. In this case, the difference between the pressure (P1) at the treated water supply port and the pressure (P3) at the back-wash wastewater discharge port is an indicator of the degree of clogging (increase in resistance) at the lower portion of the primary side of the separation membrane module, and is synonymous with R1 during the full-volume filtration process described above.

[0075] In addition, if Figure 5 As shown in (b), the 4th resistance R4 of the differential operation method 4 is a clogging index of the second separation membrane section, that is, an index indicating the degree of clogging (increase in resistance) of the separation membrane section during the back pressure washing process of the separation membrane module. The pressure (P2) of the treated water supply section is measured as the secondary side inlet side of the separation membrane module in the back pressure washing process, and the pressure (P1) of the treated water supply section is measured as the pressure (static pressure) of the primary side inlet side, and can be calculated based on their difference (ΔP4). The pressure measuring section at the primary side inlet of the separation membrane module is measured by static pressure, so it is necessary to discharge the back pressure washing wastewater from the backwash wastewater discharge section of the separation membrane module. In addition, in the case of discharging the back pressure washing wastewater from the treated water supply section, P3 can be used as the pressure measurement on the primary side inlet side of the separation membrane module, and the clogging index of the second separation membrane section can be set by calculating P3-P2.

[0076] Although not specifically limited, the upper portion of the primary side of the separation membrane module refers to the portion at least 70% of the way from the treated water supply side in the longitudinal direction of the separation membrane module (near the upper potting material), and the lower portion of the primary side of the separation membrane module refers to the portion at or below 30% of the way from the treated water supply side in the longitudinal direction of the separation membrane module (near the lower potting material). When hollow fiber membranes are used as separation membranes, the treated water supply side is often the lower side relative to gravity, so this is used here.

[0077] The clogged portion of the separation membrane module is determined by recording the changes from the initial values ​​of the indicators obtained by the above calculations in the change recording means 43-a and comparing them with the change comparing means 44-a.

[0078] Furthermore, as a specific method included in the water discharge step calculation means 46 , the pressure change rate (kPa / sec) or the water discharge flow rate (L / min) is calculated based on the measured primary side pressure in the separation membrane module.

[0079] The primary pressure (P1) during the drainage process represents the hydraulic head on the primary side of the membrane module. By calculating the primary pressure fluctuation rate, changes in the membrane module's drainage status can be understood. When the membrane module's drainage status deteriorates, the primary pressure fluctuation rate or drainage flow rate decreases. This means that turbidity stripped from the membrane during the backwash and air wash processes is not fully discharged, leading to accumulation of turbidity within the membrane module. Deterioration in the membrane module's drainage status can be broadly categorized as either due to blockage within the membrane module itself, particularly in the lower portion of the primary side, or due to the system's air intake status. In the former case, the primary pressure fluctuation rate or drainage flow rate decreases due to physical blockage in the membrane module's primary flow path. In the latter case, the primary pressure fluctuation rate or drainage flow rate decreases due to the system's configuration or when multiple membrane modules are operating. This decreases the primary pressure fluctuation rate or drainage flow rate, resulting from a decrease in air intake from the backwash drain valve 4 depending on the operating conditions of other modules. This combination, combined with calculation of the blockage location within the membrane module, allows identification of the cause of deteriorating drainage status.

[0080] Table 1 shows an outline of the operating method (clogging identification method and cleaning method) of the separation membrane module of the present invention.

[0081] [Table 1]

[0082]

[0083]

[0084] The change from the initial value of the first resistance R1 representing the resistance of the lower portion of the primary side of the separation membrane module is compared with the change from the initial value of the resistance (second resistance R2) caused by the clogging of the separation membrane of the separation membrane module and the change from the initial value of the resistance of the upper portion of the primary side of the separation membrane module (third resistance R3). Furthermore, when the change from the initial value of the first resistance R1 is the largest, or when the change from the initial value of the aforementioned first resistance R1 is larger than the set value, the blockage location determination mechanism 42 determines that the treated water supply portion and / or the lower portion of the primary side of the separation membrane module is the blockage location. Furthermore, the lower portion of the primary side of the separation membrane module is washed with emphasis compared to other locations. In addition, in the above comparison, it is not the change from the initial value of the value obtained by the above calculation, but Figure 4 As shown, the change rate is recorded in the change rate recording means 43-b, and the respective change rates are compared with each other by the change rate comparison means 44-b.

[0085] Here, the initial value refers to the first resistance R1 to the fourth resistance R4 (pressure difference, resistance value, etc.) at the time of manufacturing the separation membrane module, at the start of operation of the fresh water system, at the start of operation after chemical washing, or at the time of the last calculation process. The set value refers to the first resistance R1 to the fourth resistance R4 predetermined for determining blockage, the change amount, rate of change, etc. of the value calculated by combining these resistances. In addition, when setting the initial value and the set value, it is necessary to consider the acquisition conditions and calculation conditions of the pressure difference data (first resistance R1 to fourth resistance R4) obtained for blockage determination. For example, if the acquisition conditions (flow rate, water temperature conditions, etc.) of the initial value and the pressure difference data of the blockage determination object are the same, the pressure difference data can be compared with the initial value as it is as the first resistance R1 to the fourth resistance R4. However, if the flow rate and water temperature are different, it is preferable to set the pressure difference data or resistance value corrected to take these into account as the initial value.

[0086] For focused cleaning, it is effective to open the backwash drain valve 4 and drain valve 13 via the control mechanism 45, lower the water level until the area surrounding the primary separation membrane is filled with air, then close the drain valve 13, open the backpressure wash valve 8 and air wash valve 12, and implement at least one of the following: control a, which raises and lowers the liquid level on the primary side while performing air washing; control b, which increases the process time of the drainage step; and control c, which performs backpressure washing lower-side drainage by pressurizing the primary side of the separation membrane module with air during the drainage step, or control c, which performs backpressure washing lower-side drainage by closing the backwash drain valve 4 and opening the backpressure wash valve 8 and drain valve 13 to operate the backpressure wash pump 7. Each control can be implemented only once or multiple times. Control a can achieve a cleaning effect by eliminating bubbles at the gas-liquid interface and by significantly shaking the liquid surface due to bubble collapse, effectively cleaning the treated water supply unit and / or the lower portion of the separation membrane module.

[0087] Similarly, the change in the value obtained by the above operation from the initial value is recorded in the change recording mechanism 43-a, and with the help of the change comparison mechanism 44-a, the change in the resistance (second resistance R2) caused by the blockage of the separation membrane of the separation membrane module from the initial value, the change in the upper resistance of the separation membrane module (first resistance R1) from the initial value, and the change in the upper resistance of the separation membrane module (third resistance R3) from the initial value are compared. And, when the change in the second resistance R2 from the initial value is the largest, or when the change is larger than the set value, with the help of the blockage location determination mechanism 42, it is determined that the separation membrane is the blockage location. And, the separation membrane of the separation membrane module is washed more intensively than other locations. In addition, it may be that, in the above comparison, it is not the change in the value obtained by the above operation from the initial value, but Figure 4As shown, the change rate is recorded in the change rate recording means 43-b, and the respective change rates are compared with each other by the change rate comparison means 44-b.

[0088] Effective for focused washing are at least one of the following: control f, which operates the chemical supply pump 9 during the back-pressure washing step to supply chemical from the secondary side to the separation membrane module 3, control g, which changes at least one of the back-pressure washing time and the air wash time, and control h, which changes at least one of the back-pressure washing flow rate during the back-pressure washing step and the air wash volume during the air wash step. To further enhance the washing effect, the contact time between the chemical and the separation membrane can be adjusted. The contact time is preferably between 5 minutes and 3 hours. If the contact time is too long, the fresh water generation system 30 is shut down for a prolonged period, reducing the operating efficiency of the fresh water generation system 30. The chemical used for washing can be selected by appropriately setting the concentration and contact time to a level that prevents membrane degradation. Chemicals containing at least one of sodium hypochlorite, chlorine dioxide, hydrogen peroxide, and ozone are preferred for their enhanced cleaning effect on organic matter. Chemicals containing at least one of hydrochloric acid, sulfuric acid, nitric acid, citric acid, and oxalic acid are also preferred for their enhanced cleaning effect on aluminum, iron, manganese, and the like. The chemical concentration is preferably between 5 mg / L and 10,000 mg / L. This is because if the concentration is lower than 5 mg / L, the cleaning effect is insufficient, while if it is higher than 100,000 mg / L, the cost of the chemical solution increases, making it uneconomical. Rather than using a single chemical solution, it is preferable to use two or more chemical solutions in sequence. For example, acid and sodium hypochlorite are preferably used alternately. While the chemical solution is preferably supplied to the separation membrane module 3 from the secondary side, as in this embodiment, it is also possible to supply the chemical solution to the separation membrane module 3 from the primary side. By performing enhanced chemical cleaning, clogged separation membranes can be efficiently cleaned.

[0089] Similarly, the change in the value obtained by the above operation from the initial value is recorded in the change recording mechanism 43-a, and the change in the upper resistance of the separation membrane module (the third resistance R3) from the initial value, the change in the lower resistance of the separation membrane module (the first resistance R1) from the initial value, and the change in the resistance caused by the blockage of the separation membrane of the separation membrane module (the second resistance R2) from the initial value are compared with the change comparing mechanism 44-a. And, in the case where the change in the third resistance R3 from the initial value is the largest, or in the case where the change is larger than the set value, with the help of the blockage location determination mechanism 42, it is determined that the backwash wastewater discharge part and / or the upper part of the separation membrane module is the blockage location, and the upper part of the primary side of the separation membrane module is washed more focused than other locations. In addition, it is also possible that in the above comparison, it is not the change in the value obtained by the above operation from the initial value, but Figure 4As shown, the change rate is recorded in the change rate recording means 43-b, and the respective change rates are compared with each other by the change rate comparison means 44-b.

[0090] For focused washing, it is effective to implement at least one of the following: control d, which opens the treated water bypass valve 15, the backwash drain valve 4, and the drain valve 13 to reversely supply treated water from the nozzle that discharges the washing wastewater, and control e, which opens the drain valve 13 and the backwash drain valve 4 to drain the water from the primary side of the separation membrane module to empty it, and then operates the backpressure washing pump 7 with the backpressure washing valve 8 and the drain valve 13 open to wash the separation membrane module. Control d preferably supplies treated water as in the present embodiment, but treated water, industrial water, tap water, or RO membrane permeate water may also be used. By reversely supplying treated water from the nozzle that discharges the washing wastewater, the backwash wastewater discharge portion and / or the upper portion of the separation membrane module can be efficiently washed.

[0091] In order to determine the type of clogging of the separation membrane section, the clogging location determining means 42 further calculates the difference between the second resistance R2 and the fourth resistance R4, which are resistances caused by clogging in the separation membrane section of the separation membrane module, obtained through the calculation. If the difference (R2-R4) is greater than a set value, it is determined that clogging has occurred on the primary side surface of the separation membrane section (physical cleaning is insufficient), and the membrane surface of the separation membrane section of the separation membrane module is cleaned with priority. Alternatively, the ratio of the second resistance R2 to the fourth resistance R4 is calculated, and if the ratio (R2 / R4) is greater than a set value, the membrane surface of the separation membrane section of the separation membrane module is cleaned with priority.

[0092] As a key washing, it is effective to implement at least one of the control g for changing the back pressure washing time and the air washing time, the control h for changing the back pressure washing flow rate during the back pressure washing process and the air volume during the air washing process, and the control i for changing the water supply process time and the water supply flow rate with the help of the control mechanism 45.

[0093] Furthermore, the drainage process calculation unit 46 calculates the pressure fluctuation rate (kPa / sec) or drainage flow rate (L / min) based on the measured primary side pressure within the separation membrane module. The calculated pressure fluctuation rate (kPa / sec) or drainage flow rate (L / min) is recorded in the drainage process calculation recording unit 47 and compared with a reference value. If the value is greater than the reference value, a drainage problem is determined. The reference value here refers to the calculated value, the previous calculated value, or the set value used during the primary side pressure fluctuation rate or drainage flow rate calculation process at the start of operation of the fresh water generator or at the start of operation after chemical washing. If a drainage problem is determined and the blockage location identification unit 42 determines that the treated water supply unit and / or the lower portion of the primary side of the separation membrane module are the blockage locations, the drainage problem can be determined to be caused by blockage in the separation membrane module. If a drainage problem is determined and the blockage location identification unit 42 determines that the treated water supply unit and / or the lower portion of the primary side of the separation membrane module are not blocked, it can be determined that the abnormality has occurred at a location other than the separation membrane module, i.e., that the air intake state of the device has deteriorated during the drainage process.

[0094] The frequency of determining the blockage site and the cleaning method in the above-mentioned separation membrane module operation method is not particularly limited. However, in the case of a continuously operating fresh water system, performing the operation during each filtration cycle is preferred because it allows for early detection of blockage when it occurs. Furthermore, if the continuously operating fresh water system is configured so that the operating data necessary to determine the blockage site of the separation membrane module cannot be obtained, the extent of the blockage can be determined by replacing the separation membrane module with another separation membrane module inspection system every few weeks to years. That is, the present invention is applicable not only to automated fresh water systems but is also preferably applicable to offline inspection systems such as those operated manually. In this case, the minimum necessary operating steps are sufficient to determine the blockage site. Thereafter, the cleaning method, which is a countermeasure corresponding to the blockage site determination result, is reflected in the automatically operating fresh water system. The number of operating steps required to determine the blockage site of the separation membrane module is reduced compared to the prior art, and the calculation of operating data is also simplified, thereby reducing the work time and data calculation time of on-site operators.

[0095] In continuously operating fresh water systems, analyzing data from washing processes (back pressure washing, air washing, drainage, and water supply), which are typically performed in a shorter time relative to the filtration time, is crucial for identifying blockage sites in separation membrane modules. This requires a shorter data collection (also known as sampling, acquisition, or recording) cycle. However, due to the increased storage (recording) volume of operational data and the resulting pressure on server capacity, a shorter data recording cycle may not be feasible. Therefore, it is preferable to further provide a recording cycle setting mechanism for distinguishing operational data from the filtration process and the washing process, thereby setting different recording cycles.

[0096] The recording cycle setting mechanism can be set arbitrarily, from tens of seconds to several hours, for any filtration process. However, to prevent server capacity constraints, it is preferably set to at least one minute. However, since the washing process itself is shorter than the filtration process, data cannot be acquired within the same recording cycle as the filtration process. Therefore, it is preferably set to several seconds to several tens of seconds, and more preferably, to 5 seconds or less for data analysis used to identify blockage sites in separation membrane modules. By minimizing the amount of operational data acquired for each process, server capacity can be prevented from increasing, and communication costs can be reduced when acquiring operational data via the network.

[0097] Furthermore, for the filtration process, the operational data used to identify the blockage location is preferably data from the beginning of the filtration process, for example, preferably within 5 minutes of the start of the filtration process. In the case of a reverse pressure wash process, the resistance (R4) of the separation membrane gradually decreases during the reverse pressure wash process, so it is preferable to use operational data from the second half of the reverse pressure wash process or near its end. For example, if the reverse pressure wash process is set to 30 seconds, it is preferable to use data after 15 seconds, and more preferably after 25 seconds.

[0098] Furthermore, each of the aforementioned recording mechanisms may record not only the data of the recorded name itself but also other information that can be used to calculate the data of the recorded name. For example, a "rate of change recording mechanism" may record not only the rate of change itself but also the time intervals of measurement and the amount of change therebetween, and thus can calculate the rate of change from these data.

[0099] While various embodiments have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. A person skilled in the art will readily be able to devise various variations or modifications within the scope of the claims, and these variations or modifications will fall within the technical scope of the present invention. Furthermore, the various structural elements of the above embodiments may be arbitrarily combined without departing from the spirit of the invention.

[0100] In addition, this application is based on the Japanese patent application (Japanese Patent Application No. 2020-129968) for which it applied on July 31, 2020, and the content is cited in this application as a reference.

[0101] Description of Reference Numerals

[0102] 1: Treated water supply pump

[0103] 2: Treated water supply valve

[0104] 3: Separation membrane module

[0105] 3a: Lower part of the primary side of the separation membrane module

[0106] 3b: Upper part of the primary side of the separation membrane module

[0107] 4: Backwash drain valve

[0108] 5: Process water discharge valve

[0109] 6: Treated water storage tank

[0110] 7: Back pressure washing pump

[0111] 8: Back pressure washing valve

[0112] 9: Liquid supply pump

[0113] 10: Liquid storage tank

[0114] 11: Blower

[0115] 12: Air washing valve

[0116] 13: Drain valve

[0117] 14: Treated water supply valve to the primary side

[0118] 15: Treated water bypass valve

[0119] 16: Primary side supply pressure sensor

[0120] 17: Primary side outlet pressure sensor (P3)

[0121] 18: Secondary side pressure sensor (P2)

[0122] 19: Drain flow sensor

[0123] 20: Cylindrical shell

[0124] 21: Separation membrane (hollow fiber membrane)

[0125] 22: Potting material

[0126] 23: Hat

[0127] 24: Lower side nozzle

[0128] 25: Upper side nozzle (backwash wastewater discharge part)

[0129] 26: Upper nozzle (treated water discharge part)

[0130] 27: Lower nozzle (treated water supply part)

[0131] 28: Through hole

[0132] 30: Water making system

[0133] 31: Computer

[0134] 32: Blockage Location Determination Procedure

[0135] 40: Operation data recording mechanism

[0136] 41: Differential operation mechanism

[0137] 42: Blockage location determination mechanism

[0138] 43-a: Change recording mechanism

[0139] 43-b: Rate of Change Recording Mechanism

[0140] 44-a: Change comparison mechanism

[0141] 44-b: Change rate comparison mechanism

[0142] 45: Control mechanism

[0143] 46: Drainage process calculation mechanism

[0144] 47: Drainage process calculation and recording mechanism

Claims

1. A method for operating a separation membrane module, wherein, in a fresh water production system in which treated water is obtained by filtering treated water through the separation membrane module, a blockage location in the separation membrane module is determined based on resistance at a lower portion of the separation membrane module, filtration resistance at a separation membrane portion, and resistance at an upper portion of the separation membrane module; The method for operating the separation membrane module is characterized in that: The separation membrane module is composed of a cylindrical shell with a separation membrane inserted therein. A treated water supply portion for supplying the treated water is provided at the lower portion of the separation membrane module as the primary side, a treated water discharge portion for discharging the treated water is provided at the upper portion as the secondary side, and a backwash wastewater discharge portion for discharging backpressure washing wastewater is provided at the upper portion of the side surface of the cylindrical shell as the primary side, which is connected to the outside of the separation membrane. The fresh water generation system includes a supply pressure sensor for measuring the pressure P1 of the treated water supply section, a secondary side pressure sensor for measuring the pressure P2 of the treated water discharge section, and a primary side outlet pressure sensor for measuring the pressure P3 of the backwash wastewater discharge section. The pressure difference ΔP1 between P1 and P3 in the filtration process of filtering the water to be treated from the primary side to the secondary side of the separation membrane module is defined as the first resistance R1. The pressure difference ΔP2 between the P3 and P2 in the filtration step is defined as the second resistance R2. The calculation is performed by setting the pressure difference ΔP3 between P1 and P3 in the back pressure washing process of pressure feeding from the secondary side to the primary side of the separation membrane module as the third resistance R3. The clogged portion of the separation membrane module is determined based on the amount of change or rate of change of each of the first to third resistances R1 to R3 obtained by calculation from the initial value.

2. The method for operating a separation membrane module according to claim 1, wherein: The P3 in the filtration step and the P1 in the back pressure washing step are static pressure.

3. The method for operating a separation membrane module according to claim 1 or 2, wherein: Comparing the respective amounts of change from the initial value of the first resistance R1, the second resistance R2, and the third resistance R3, if the amount of change from the initial value of the first resistance R1 is greater than the amounts of change from the initial value of the second resistance R2 and the amounts of change from the initial value of the third resistance R3, or if the amount of change from the initial value of the first resistance R1 is greater than the set value, at least one of the following controls A to C is performed: A controls the liquid level on the primary side of the separation membrane module to rise and fall and performs air scrubbing; B. Control that lengthens the drainage process time; C. Control of pressurized drainage in which the primary side of the separation membrane module is pressurized with air to drain water during the drainage step.

4. The method for operating a separation membrane module according to claim 1 or 2, wherein: The rates of change of the first resistance R1, the second resistance R2, and the third resistance R3 from their initial values ​​are compared. If the rate of change of the first resistance R1 from its initial value is greater than the rates of change of the second resistance R2 and the third resistance R3 from their initial values, or if the rate of change of the first resistance R1 from its initial value is greater than a set value, at least one of the following controls A to C is performed. A controls the liquid level on the primary side of the separation membrane module to rise and fall and performs air scrubbing; B. Control that lengthens the drainage process time; C. Control of pressurized drainage in which the primary side of the separation membrane module is pressurized with air to drain water during the drainage step.

5. The method for operating a separation membrane module according to claim 1 or 2, wherein: Comparing the respective amounts of change from the initial value of the first resistance R1, the second resistance R2, and the third resistance R3, if the amount of change from the initial value of the second resistance R2 is greater than the amounts of change from the initial value of the first resistance R1 and the amounts of change from the initial value of the third resistance R3, or if the amount of change from the initial value of the second resistance R2 is greater than the set value, at least one of the following controls F to H is performed: F supplies a chemical solution to the separation membrane module to implement the control of washing the separation membrane module; G. Control of changing at least one of the reverse pressure washing time and the air washing time; H is a control to change at least one of the back pressure washing flow rate during the back pressure washing process and the air volume during the air washing process.

6. The method for operating a separation membrane module according to claim 1 or 2, wherein: The rates of change of the first resistance R1, the second resistance R2, and the third resistance R3 from their initial values ​​are compared. If the rate of change of the second resistance R2 from its initial value is greater than the rates of change of the first resistance R1 and the third resistance R3 from their initial values, or if the rate of change of the second resistance R2 from its initial value is greater than a set value, at least one of the following controls F to H is performed. F supplies a chemical solution to the separation membrane module to implement the control of washing the separation membrane module; G. Control of changing at least one of the reverse pressure washing time and the air washing time; H is a control to change at least one of the back pressure washing flow rate during the back pressure washing process and the air volume during the air washing process.

7. The method for operating a separation membrane module according to claim 1 or 2, wherein: Comparing the respective amounts of change from the initial value of the first resistance R1, the second resistance R2, and the third resistance R3, if the amount of change from the initial value of the third resistance R3 is greater than the amounts of change from the initial value of the first resistance R1 and the amounts of change from the initial value of the second resistance R2, or if the amount of change from the initial value of the third resistance R3 is greater than the set value, performing at least one of the following controls D to E: D. Control of reverse supply of treated water from the nozzle that discharges the washing wastewater of the separation membrane module; E. Control of back pressure washing after draining the water from the primary side of the separation membrane module to empty it.

8. The method for operating a separation membrane module according to claim 1 or 2, wherein: Comparing the respective rates of change of the first resistance R1, the second resistance R2, and the third resistance R3 from their initial values, and when the rate of change of the third resistance R3 from its initial value is greater than the rates of change of the first resistance R1 and the second resistance R2 from their initial values, or when the rate of change of the third resistance R3 from its initial value is greater than a set value, performing at least one of the following controls D to E: D. Control of reverse supply of treated water from the nozzle that discharges the washing wastewater of the separation membrane module; E. Control of back pressure washing after draining the water from the primary side of the separation membrane module to empty it.

9. The method for operating a separation membrane module according to claim 1 or 2, wherein: At least one of the primary side pressure change rate and drainage flow rate selected from the separation membrane module in the drainage process is used as an indicator and combined with the aforementioned first resistance R1, the aforementioned second resistance R2, and the aforementioned third resistance R3 to determine the blockage location of the aforementioned separation membrane module. The aforementioned drainage process discharges the treated water from the lower part of the primary side of the separation membrane module to the outside of the system.

10. The method for operating a separation membrane module according to claim 1 or 2, wherein: The pressure difference ΔP4 between the pressures P2 and P1 in the back pressure washing step is further calculated as the fourth resistance R4. When the difference R2-R4 between the second resistance R2 and the fourth resistance R4 is greater than a set value, or when the ratio R2 / R4 between the second resistance R2 and the fourth resistance R4 is greater than a set value, at least one of the following controls G to I is performed: G. Control of changing at least one of the reverse pressure washing time and the air washing time; H. Control of changing at least one of the back pressure washing flow rate during the back pressure washing process and the air volume during the air washing process; I. Control of changing at least one of the water supply process time and water supply flow rate.

11. The method for operating a separation membrane module according to claim 10, wherein: The filtration flow rate during the aforementioned filtration step and the backwash flow rate during the aforementioned backpressure washing step are the same.

12. The method for operating a separation membrane module according to claim 10, wherein: The second resistance R2 and the fourth resistance R4 are resistance values ​​calculated based on the pressure difference, flow rate data, and water temperature data.

13. A computer-readable recording medium having a fresh water production system management program recorded thereon, wherein the computer functions as a blockage location determining mechanism for determining the blockage location of a separation membrane module in a fresh water production system that obtains treated water by filtering treated water through the separation membrane module, the computer functioning as a blockage location determining mechanism for determining the blockage location of the separation membrane module based on resistance at the bottom of the separation membrane module, filtration resistance at the separation membrane portion, and resistance at the top of the separation membrane module. The computer-readable recording medium having the water generation system management program recorded thereon is characterized in that: The separation membrane module is composed of a cylindrical shell with a separation membrane inserted therein. A treated water supply portion for supplying the treated water is provided at the lower portion of the separation membrane module as the primary side, a treated water discharge portion for discharging the treated water is provided at the upper portion as the secondary side, and a backwash wastewater discharge portion for discharging backpressure washing wastewater is provided at the upper portion of the side surface of the cylindrical shell as the primary side, which is connected to the outside of the separation membrane. The fresh water generation system includes a supply pressure sensor for measuring the pressure P1 of the treated water supply section, a secondary side pressure sensor for measuring the pressure P2 of the treated water discharge section, and a primary side outlet pressure sensor for measuring the pressure P3 of the backwash wastewater discharge section. The computer is made to function as a differential calculation unit and a blockage site determination unit. The differential calculation mechanism sets the pressure difference ΔP1 between the P1 and P3 in the filtration process of filtering the water to be treated from the primary side to the secondary side of the separation membrane module as the first resistance R1. The pressure difference ΔP2 between the P3 and P2 in the filtration step is defined as the second resistance R2. The calculation is performed by setting the pressure difference ΔP3 between P1 and P3 in the back pressure washing process of pressure feeding from the secondary side to the primary side of the separation membrane module as the third resistance R3. The clogging location identifying means identifies the clogging location of the separation membrane module based on an amount of change or a rate of change of each value obtained by the difference calculating means from an initial value.

14. The computer-readable recording medium having a water generation system management program recorded thereon according to claim 13, wherein: The P3 in the filtration step and the P1 in the back pressure washing step are static pressure.

15. A fresh water production system, wherein a computer functions as a blockage location determining means for determining the blockage location of a separation membrane module of the fresh water production system, wherein the computer determines the blockage location of the separation membrane module based on the resistance at the bottom of the separation membrane module, the filtration resistance at the separation membrane section, and the resistance at the top of the separation membrane module, in order to determine the blockage location of the separation membrane module of the fresh water production system, wherein the separation membrane module filters treated water to be treated by the separation membrane module. The above-mentioned water generation system is characterized in that: The separation membrane module is composed of a cylindrical shell with a separation membrane inserted therein. A treated water supply portion for supplying the treated water is provided at the lower portion of the separation membrane module as the primary side, a treated water discharge portion for discharging the treated water is provided at the upper portion as the secondary side, and a backwash wastewater discharge portion for discharging backpressure washing wastewater is provided at the upper portion of the side surface of the cylindrical shell as the primary side, which is connected to the outside of the separation membrane. The fresh water generation system includes a supply pressure sensor for measuring the pressure P1 of the treated water supply section, a secondary side pressure sensor for measuring the pressure P2 of the treated water discharge section, and a primary side outlet pressure sensor for measuring the pressure P3 of the backwash wastewater discharge section. The computer is made to function as a differential calculation unit and a blockage site determination unit. The differential calculation mechanism sets the pressure difference ΔP1 between the P1 and P3 in the filtration process of filtering the water to be treated from the primary side to the secondary side of the separation membrane module as the first resistance R1. The pressure difference ΔP2 between the P3 and P2 in the filtration step is defined as the second resistance R2. The calculation is performed by setting the pressure difference ΔP3 between P1 and P3 in the back pressure washing process of pressure feeding from the secondary side to the primary side of the separation membrane module as the third resistance R3. The blockage location identifying means identifies the blockage location of the separation membrane module based on the amount of change or rate of change of each of the first to third resistances R1 to R3 obtained by the difference calculating means from an initial value.

16. The water generation system according to claim 15, wherein: The P3 in the filtration step and the P1 in the back pressure washing step are static pressure.

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